Research On The Electric Hydraulic Power Steering System With Auxiliary Accumulator

At present,it is difficult for the constant flow EHPS system used in small and medium-sized vehicles to coordinate the contradiction between improving the power response characteristics and reducing the motor energy consumption.The pipeline of constant pressure EHPS system used in large and medium-sized vehicles is always under high pressure,leading to serious internal leakage of the system and severely affecting the service life of hydraulic components.Aiming at the above problems,based on the constant flow EHPS system of model A pure electric bus,a technical scheme of EHPS system with auxiliary accumulator is proposed,in which the response characteristics of the system is improve and the energy consumption of the motor is reduced.The main research work is as follows:1.The problems of the constant flow EHPS system of model A pure electric bus is analyzed and the technical scheme of EHPS system with auxiliary accumulator is put forward,in which the accumulator and other components are added to the original EHPS system.The motor stops working under the non steering condition of vehicles,and the energy consumption of the system is reduced.In the speed response phase of the motor in the steering condition,the accumulator works to ensure and improve the power response characteristics of the system.2.Based on the relevant parameters and the test results of steering resistance moment vehicle test of model A pure electric bus,the relationship model of steering resistance moment with vehicle speed and steering wheel angle of model A pure electric bus under full load condition is established in Matlab / Simulink.The relationship between ideal steering hand force and vehicle speed and steering wheel angle is determined.According to the working characteristics of the steering control valve and accumulator,and the relationship between the flow of hydraulic pump and the speed of the motor,the relationship between the speed of the motor and the steering torque is determined.Based on the relationship among the steering resistance moment,ideal steering hand force and steering assistant moment,the MAP diagram of the power assisted characteristics of EHPS with auxiliary accumulator system of model A pure electric bus under full load condition is established.3.The model of EHPS system with auxiliary accumulator is established in MATLAB / Simulink and AMESim,and the response characteristics,follow-up and stability of the motor are simulated and analyzed.Based on the simulation results of the motor,the response characteristics of the system under different accumulator precharge pressure and volume are simulated,and the volume of the accumulator and the precharge pressure under various working conditions are determined.The steering portability,power following and the response characteristics of the steering wheel angle step input of the system are simulated and analyzed;The energy saving performance of the power motor of the improved system is calculated and analyzed.The simulation results show that the EHPS system with auxiliary accumulator ensures the portability of low-speed steering and the road sense of the driver in high-speed steering,improves the response characteristics of the booster and reduces the energy consumption of the booster motor.